Press heads



Aug. 16, 1966 E. IVARSSON 3,266,103

PRESS HEADS Filed May a, 1964 2 Sheets-Sheet 1 fare/27w Aug. 16, 1966 E. IVARSSON 3,266,193

PRESS HEADS Filed May 8, 1964 2 Sheets-Sheet 2 rh/i vlK

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United States Patent 3,266,103 PRESS HEADS Erik Ivarsson, Halmstad, Sweden, assignor to Aktiebolaget Malcus Holmquist, Halmstad, Sweden, a corporation of Sweden Filed May 8, 1964, Ser. No. 366,008 Claims priority, application Sweden, May 14, 1963 5,318/ 63 6 Claims. (Cl. 2246) The present invention relates to a press head for pressing the sand in mould flasks in mechanical mould production in which the mould flask and the model are placed on the vibrating table of the moulding machine which table after the filling of the mould flask with sand is raised towards the press head for compressing the sand.

The object of the invention is to obtain a press head which ensures a very uniform pressing of the sand but in spite of this is simple and reliable in operation.

This is according to the invention obtained therein that the press head is provided with a number of vertically arranged cylinders the upper ends of which communicate with each other and form a closed hydraulic system and each of which is provided with a piston connected to the upper end of a piston rod which projects from the lower end of the cylinder and at its projecting end is provided with a press plate, in the rest position the pistons of all cylinders being adapted to be held in neutral position at about the middle of the length of the cylinders, e.g. by means of springs or the like.

The invention will be further described in connection to the embodiment shown on the attached drawings.

FIG. 1 shows a side view of a moulding machine provided with a press head according to the invent-ion.

FIG. 2 shows in side view and partly in section the press head during the compression of the sand in a mould flask.

FIG. 1 shows a moulding machine having a frame 10, a press head 13, and a vibrating table 11 which by means of a diagrammatically shown pneumatic working cylinder '12 can be raised towards the press head 13 of the moulding machine.

As shown in FIG. 2 the press head comprises a closed container 14 provided with filling plugs 15 and filled with a suitable liquid e.g. hydraulic oil. From the lower side of the container 14 several vertical cylinders 16 project downwardly, each of said cylinders being in communication with the interior of the container 14 and connected to said container e.g. by means of bolts. Suitable sealing means 17 prevent leak-age through the connections between the cylinders and the container. Each cylinder 16 is provided with a piston 18 movable therein and provided with suitable sealing means. The piston 18 is attached to the upper end of a piston rod 19 projecting downwardly through the lower end of the cylinder *16 and at its lower end provided with a press plate 20 e.g. of rectangular shape, the lower side of which may have the shape of a very blunt-ended inverted pyramid. Between the lower side of the piston 18 and an annular shoulder 21 within the cylinder =16 there is provided a compression spring 22 around the piston rod 19 which spring serves to maintain the piston 18 in a neutral position about the middle of the cylinder 16. The downwardly projecting end of the piston rod 1-9 is surrounded by a bellows 23 of rubber or similar material.

The function of the press head is as follows:

When the mould flask 24 together with the pattern 25 has been placed onto the vibrating table of the moulding machine and when the mould flask has been filled with sand 26 compressed air is supplied to the working or lifting cylinder 12 which then raises the vibrating table 11 upwardly towards the press head 13. Those press plates 3,266,103 Patented August 16, 1966 20 which first come into contact with the sand are thereby raised slightly and thus the corresponding pistons 18 are moved .upwardly from their neutral position. The hydraulic oil in the upper ends of these cylinders is forced out from these cylinders in some degree and as the liquid system is completely closed a corresponding amount of oil flows into the remaining cylinders and move the pistons 18 therein downwards. After all press plates 20 have come into contact with the sand and the raising of the vibrating table is continued somewhat a very uniform compression of the sand is obtained below each press plate 20 due to the fact that all cylinders 16 communicate with each other via the container 14 and thus the pressures in the cylinders are equal. When the vibration table 1'1 then is lowered the pistons 18 return to their neutral positions so that the press plates 20 automatically return substantially to a common plane.

In the shown and described embodiment the pistons 18 have substantially the same piston areas and also the pressure plates are substantially of the same size (the outermost press plates .in FIG. 2 are turned in relation to the remaining plates). However the device can also be constructed so that with equal size of the press plates certain pistons are provided with increased piston area so that the compression of the sand within certain parts of the mould flask becomes stronger or if the piston areas are unchanged in size some of the press plates can be made smaller which also results in an increased compression of the sand below these smaller plates.

in the connections between the cylinders 16 there may be inserted throttling means which are here exemplified by the plates 27 having restricted orifices 28 therein through which the hydraulic fluid is require-d to pass to thus exert a damping action to insure steady movements of the pistons. In addition, if desired, an auxiliary container 29 may be connected to the hydraulic system by way of a conduit 30 having a conventional non-return valve 3'1 therein for making it possible to replenish the system. The auxiliary container 29 may comprise the cylinder of a conventional working cylinder or cylinder and piston unit which, as fragmentarily illustrated in FIGURE 2, comprises a piston 32 of relatively small area adapted to have pressure applied thereto in conven tional manner through its piston rod 33 for delivering fluid at high pressure past the one-way valve 31 and to the hydraulic system so that after the press plates are uniformly in contact with the sand and equilibrium has been obtained a considerable increase of the pressure in the hydraulic system can be obtained by a small output of power and thus ensure a strong and uniformly distributed compression pressure onto the sand.

Modifications and detail changes are possible within the scope of the invention as stated in the attached claims.

I claim:

1. A moulding machine comprising a press head and means supporting same in a vertically-fixed position, a table beneath said press head for supporting a mould flask filled with moulding sand, means for moving the said table vertically toward said head for compressing the sand within the flask, the improvement in accordance with which said press head comprises a plurality of verticallydisposed cylinders each having a piston disposed for vertical movement therein, a piston rod depending from each piston through the lower end of its respective cylinder, a press plate carried at the lower end of each said piston rod for reception in said flask in pressing engagement with the sand therein, means normally urging the respective pistons to positions of rest intermediate of the ends of their respective cylinders, said cylinders being interconnected above their respective pistons to define a closed normally-constant voilume hydraulic system operative during said vertical movement of the table toward the press head for utilizing the resulting upwand displacement of those presser plates which initially engage the sand in said flask for transmitting fluid pressure to the pistons of other said presser plates for projecting the latter downwardly into engagement with the said sand, and for maintaining a fixed relation between the maximum pressures exerted by the respective plates when all of them engage the sand.

2. A moulding machine as defined in claim 1, wherein said means nonmally urging the respective pistons to their positions of rest comprises resilient means in the respective cylinders urging said pistons upwardly together with port-ions of the liquid of the closed system normally retained within each cylinder above its piston and maintaining a balancing pressure thereagainst in opposition to said means in the respective cylinders, the v olume of said liquid and the strength of said resilient means being selected to urge the respective pistons when disengaged from the sand toward positions in a common horizontal plane substantially midway of and spaced from the opposite axia'l ends of their respective cylinders.

3. A moulding machine according to claim 1, characterized in that said hydraulic system includes a closed container, said cylinders being afiixed to and depending from said container with their upper ends in free communication with said container.

4. A moulding machine according to claim 1, characterized in that throttling means are provided in the connections between the cylinders and their connections to the container respectively.

5 A moulding machine according to claim 1, characterized in that a working cylinder with small piston area is connected to the hydraulic system which cylinder is intended to be used to increase the pressure.

6. A moulding machine according to claim -1, char acterized in that the hydraulic system is connected to an auxiliary container via a non return valve for replenishing the system.

References Cited by the Examiner UNITED STATES PATENTS 318,784 5/ 1885 Moore 2225 364,948 6/1887 Moore 22--41 382,217l 5/1888 Davies 224l 450,521 4/ 1891 Mistelski 224-1 3,181,208 5/1965 Brauer 22-41 I. SPENCER OVERHOLSER, Primary Examiner.

MARCUS U. LYONS. Examiner. 

1. A MOULDING MACHINE COMPRISING A PRESS HEAD AND MEANS SUPPORTING SAME IN A VERTICALLY-FIXED POSITION, A TABLE BENEATH SAID PRESS HEAD FOR SUPPORTING A MOULD FLASK FILLED WITH MOULDING SAND, MEANS FOR MOVING THE SAID TABLE VERTICALLY TOWARD SAID HEAD FOR COMPRESSING THE SAND WITHIN THE FLASK, THE IMPROVEMENT IN ACCORDANCE WITH WHICH SAID PRESS HEAD COMPRISES A PLURALITY OF VERTICALLYDISPOSED CYLINDERS EACH HAVING A PISTON DISPOSED FOR VERTICAL MOVEMENT THEREIN, A PISTON ROD DEPENDING FROM EACH PISTON THROUGH THE LOWER END OF ITS RESPECTIVE CYLINDER, A PRESS PLATE CARRIED AT THE LOWER END OF EACH SAID PISTON ROD FOR RECEPTION IN SAID FLASK IN PRESSING ENGAGEMENT WITH THE SAND THEREIN, MEANS NORMALLY URGING THE RESPECTIVE PISTONS TO POSITIONS OF REST INTERMEDIATE OF THE ENDS OF THEIR RESPECTIVE CYLINDERS, SAID CYLINDERS BEING INTER- 